Method for inhibiting cyanide elution and material for inhibiting cyanide elution

Abstract

To provide a new method for easily inhibiting cyanide elution in drainage, soil or the like.SOLUTION: A method for inhibiting cyanogen elution includes a blending process of blending a material to be treated and a cyanogen elution inhibitor. The cyanogen elution inhibitor is characterized by including at least one selected from the group consisting of the burned material of a below-mentioned component (A), that of a below-mentioned component (B) or that of a mixture including the components (A) and (B). Here, the component (A) is at least one selected from Ca(OH)2, CaCO3, CaCl2, Ca(NO3)2 and CaO, and the component (B) is at least one selected from Al(OH)3, Al2(SO4)3 and Al2O3. Further, the material to be treated is characterized by being the water-based or soil-based material including cyanide.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a method for suppressing cyanide elution and a material for suppressing cyanide elution. [Background technology]

[0002] Since wastewater and soil contain various harmful substances, technologies for removing them or suppressing their elution have been developed and put to practical use. Among the harmful substances, hexavalent chromium, boron, etc., are adsorbed and fixed on an adsorbent such as zeolite, thereby preventing contamination due to diffusion. However, among harmful substances, cyanide is difficult to adsorb on an adsorbent used for other harmful substances, and it is extremely difficult to remove or prevent diffusion. For example, in the case of wastewater containing cyanide, it must be decomposed to N2 and NaCl in a two-stage reaction by oxidative decomposition using sodium hypochlorite under alkaline conditions (Non-Patent Document 1). In this method, cyanide is oxidized to cyanic acid in a high pH state in the first reaction, and then the pH is adjusted to near neutral in the second reaction to decompose the cyanic acid to N2 and NaCl, which is time-consuming. In addition, this method is difficult to apply to the treatment of soil, etc. [Prior art documents] [Non-patent literature]

[0003] [Non-Patent Document 1] Water Recycling and Wastewater Treatment Technology - Latest Trends by Technology Field and by Wastewater and Wastewater Type, Toray Research Center, Inc., Research and Development Division, 2007 Summary of the Invention [Problem to be solved by the invention]

[0004] Therefore, an object of the present invention is to provide a new method for easily suppressing the elution of cyanide into wastewater, soil, etc. [Means for solving the problem]

[0005] In order to achieve the above object, a method for suppressing cyanide elution of the present invention includes a mixing step of mixing an object to be treated with a cyanide elution suppression material, The cyanide elution inhibitor includes at least one calcined product selected from the group consisting of a calcined product of the following component (A), a calcined product of the following component (B), or a calcined product of a mixture containing the following component (A) and the following component (B), The object to be treated is characterized in that it is an aqueous or soil-based object to be treated that contains cyanide. Component (A): At least one component selected from the group consisting of Ca(OH)2, CaCO3, CaCl2, Ca(NO3)2, and CaO Component (B): at least one component selected from the group consisting of Al(OH)3, Al2(SO4)3, and Al2O3

[0006] The cyanide elution inhibitor of the present invention is characterized in that it contains at least one calcined product selected from the group consisting of a calcined product of the following component (A), a calcined product of the following component (B), or a calcined product of a mixture containing the following component (A) and component (B): Component (A): At least one component selected from the group consisting of Ca(OH)2, CaCO3, CaCl2, Ca(NO3)2, and CaO Component (B): at least one component selected from the group consisting of Al(OH)3, Al2(SO4)3, and Al2O3 Effect of the Invention

[0007] According to the method for inhibiting cyanide elution of the present invention, the elution of cyanide in a material to be treated can be easily inhibited by simply mixing the material to be treated with the cyanide elution-inhibiting material. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a graph showing the relationship between the Ca / Al molar ratio in a Ca—Al compound and the amount of cyanide ions removed in Example 1. [Diagram 2]FIG. 2 is a graph showing, on the left, the relationship between the amount of cyanide ions removed per 1 g of Ca-Al compound in Example 1 and the concentration of cyanide ions remaining in the aqueous cyanide solution after the treatment, and a graph showing, on the right, the relationship between the amount of cyanide ions removed per 1 g of Ca-Al compound in Example 1 and the initial concentration of cyanide ions in the aqueous cyanide solution. [Diagram 3] FIG. 3 is a graph showing the results of X-ray diffraction on the precipitate formed after treating the aqueous cyanide solution with a Ca—Al compound in Example 1. [Figure 4] FIG. 4 is a graph showing the results of X-ray diffraction on the precipitate after mixing water and a Ca—Al compound in Example 1. [Diagram 5] FIG. 5 is a graph showing the results of X-ray diffraction on the precipitate obtained after treating the aqueous cyanide solution with a Ca—Al compound in Example 1. [Figure 6] FIG. 6 is a graph showing the concentration of cyanide ions eluted from the contaminated sand treated with a Ca—Al compound in Example 2. [Figure 7] FIG. 7 is a graph showing the concentration of cyanide ions eluted from the contaminated sand treated with a Ca—Al compound in Example 2. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] In the method for suppressing cyanide elution of the present invention, the material to be treated is, for example, wastewater, soil, or sludge.

[0010] In the method for suppressing cyanide elution of the present invention, for example, the cyanide to be suppressed from eluting is a cyanide ion.

[0011] In the method for inhibiting cyanide elution of the present invention, the molar ratio of Ca to Al (Ca / Al) in the fired product is in the range of 0.5 to 15, for example.

[0012] In the method for inhibiting cyanide elution of the present invention, for example, in the mixing step, 100 parts by mass of the material to be treated is mixed with 1 to 60 parts by mass of the baked material.

[0013] In the method for inhibiting cyanide elution of the present invention, the molar ratio of Ca to Al (Ca / Al) in the fired product is in the range of 0.5 to 5, for example.

[0014] In the method for inhibiting cyanide elution of the present invention, for example, in the mixing step, 100 parts by mass of the material to be treated is mixed with 1 to 30 parts by mass of the baked material.

[0015] In the method for suppressing cyanide elution of the present invention, for example, the calcined product is a calcined product of a mixture containing the component (A) and the component (B), the component (A) is at least one of Ca(OH)2 and CaCO3, and the component (B) is Al(OH)3.

[0016] In the method for suppressing cyanide elution of the present invention, for example, the calcined product is CaO, Al2O3, CaAl2O4, Ca5Al6O 14 , Ca9Al6O 18 , and Ca 12 Al 14 O 33 The composition comprises at least one crystalline compound selected from the group consisting of:

[0017] Hereinafter, an embodiment of the present invention will be described. However, the present invention is not limited to the following embodiment.

[0018] As described above, the method for inhibiting cyanide elution of the present invention includes a mixing step of mixing a material to be treated with a cyanide elution inhibitor, and the cyanide elution inhibitor includes at least one calcined product selected from the group consisting of a calcined product of the following component (A), a calcined product of the following component (B), or a calcined product of a mixture containing the following component (A) and component (B), and the material to be treated is an aqueous or soil-based material containing a cyanide. Component (A): At least one component selected from the group consisting of Ca(OH)2, CaCO3, CaCl2, Ca(NO3)2, and CaO Component (B): at least one component selected from the group consisting of Al(OH)3, Al2(SO4)3, and Al2O3

[0019] In the present invention, the "material to be treated that contains cyanide" may be, for example, a material that actually contains cyanide or a material that may contain cyanide. The aqueous material to be treated is, for example, wastewater, wastewater, etc. The earth-based material to be treated is, for example, soil, mud, etc., and specifically, for example, materials collected from the ground, mountains, seabed, etc.

[0020] In the present invention, the cyanide is, for example, a compound having a -CN (cyano group), and specifically, for example, a cyanide ion (CN - ) is a salt having the above structure. The cyanide exists as a cyanide ion in the treated material, for example, in the presence of water. According to the method for inhibiting cyanide elution of the present invention, for example, the calcined product insolubilizes the cyanide ion in the treated material, thereby inhibiting the elution from the treated material to the outside. Therefore, the method for inhibiting cyanide elution of the present invention can be called, for example, a method for insolubilizing cyanide or a method for inhibiting diffusion of cyanide. In the present invention, insolubilization means that, when the treated material is an earth-based material, for example, even if the treated material is mixed with the cyanide elution inhibitor and water penetrates the mixture, the cyanide can be inhibited from dissolving in the water, thereby inhibiting the cyanide from flowing out of the mixture together with water. In addition, when the treated material is an aqueous material, for example, the cyanide is insolubilized by mixing the aqueous material in which the cyanide is dissolved with the cyanide elution inhibitor, thereby inhibiting the insolubilized cyanide from re-dissolving in the aqueous material.

[0021] The cyanide elution inhibitor may contain any one of the calcined products, and other components are not limited thereto. The cyanide elution inhibitor may contain only the calcined product, or may contain other components in addition to the calcined product, as long as the effects of the calcined product are not impaired.

[0022] Hereinafter, the calcined product of the (A) component is referred to as the calcined product A, the calcined product of the (B) component is referred to as the calcined product B, and the calcined product of the mixture containing the (A) component and the (B) component (hereinafter also referred to as the mixture (AB)) is referred to as the mixed calcined product AB. The cyanide elution inhibitor may contain, for example, only the calcined product A, only the calcined product B, both the calcined product A and the calcined product B, only the mixed calcined product AB, or both the mixed calcined product AB and the calcined product A, the calcined product B, or both the calcined product A and the calcined product B. Among these, the cyanide elution inhibitor preferably contains, for example, the mixed calcined product AB as the calcined product.

[0023] In the cyanide elution inhibitor, the ratio of Ca and Al derived from the calcined product is not particularly limited, and the molar ratio of Ca to Al (Ca / Al) is, for example, 0.5 to 15, 1 to 10, or 1 to 5. Since the amount of the calcined product added to the object to be treated can be relatively reduced, the molar ratio of Ca to Al (Ca / Al) is preferably, for example, 2±1. On the other hand, when it is outside this range, for example, by relatively increasing the amount of the calcined product added, it is possible to realize the same inhibition of cyanide elution as with the calcined product within the above range.

[0024] In the cyanide elution inhibitor, the (A) component is preferably at least one of Ca(OH)2 and CaCO3, and the (B) component is preferably Al(OH)3. In addition, in the cyanide elution inhibitor, the calcined product is preferably the mixed calcined product AB, and in this case, the mixed calcined product AB of the mixture (AB) containing the (A) component of at least one of Ca(OH)2 and CaCO3 and the (B) component of Al(OH)3 is preferable.

[0025] The simple substance A may be, for example, a crystalline compound such as CaO. When the cyanide elution inhibitor contains the simple substance A, the type of the simple substance A may be, for example, one type or two or more types. When the cyanide elution inhibitor contains the simple substance B, the type of the simple substance B may be, for example, one type or two or more types.

[0026] The mixed calcined product AB is, for example, CaO, Al2O3, CaAl2O4, Ca5Al6O 14 , Ca9Al6O 18 , and Ca 12 Al 14 O 33 The calcined product can be, for example, hydrocalumite (Ca4Al2(OH) 14 .6H2O), specifically, CaO, Al2O3, CaAl2O4, Ca5Al6O 14 , Ca9Al6O 18 , and Ca 12 Al 14 O 33 etc. In the case where the cyanide elution inhibitor contains the mixed calcined product AB, the type may be one or more. The crystalline compound is produced by a chemical reaction by calcining a mixture (AB) of the (A) component and the (B) component. The mixed calcined product AB can have a composition of the crystalline compound that can be changed by, for example, the ratio (molar ratio) of the (A) component to the (B) component used, the calcination temperature, etc.

[0027] The fired product A, the fired product B, and the mixed fired product AB can be produced, for example, by firing the component (A), the component (B), or the mixture (AB). The firing temperature is not particularly limited, and the lower limit is, for example, 600°C or more, 800°C or more, and the upper limit is, for example, 1200°C or less, 1000°C or less.

[0028] As described above, the cyanide elution inhibitor may contain other components, and examples of the other components include an adsorbent that adsorbs ions of heavy metals and the like.

[0029] As described above, in the method for suppressing cyanide elution of the present invention, the material to be treated and the cyanide elution-suppressing material are mixed in the mixing step.

[0030] The hydrocalumite can be formed, for example, by a mixing reaction between the calcined product and water. For this reason, when mixing with the material to be treated, for example, the calcined product of the cyanide elution inhibitor is preferably coexistent with water. When the material to be treated is water-based, the water may be, for example, the material to be treated itself, and when the material to be treated is earth-based, the water may be, for example, the moisture contained in the earth-based material to be treated, or may be water added. The calcined product may be coexistent with water, for example, before mixing with the material to be treated, or may be coexistent with water when mixed with the material to be treated. The ratio of the calcined product to water is not particularly limited, and for example, it is preferable that the calcined product is 1 time or more, 1.2 times or more, or 1.4 times or more by weight relative to 1 water, and when the molar ratio (Ca / Al) of Ca to Al in the calcined product is 2, for example, it is preferable that the calcined product is 1.4 times or more by weight relative to 1 water.

[0031] When the material to be treated is aqueous, the material can be treated by adding the cyanide elution suppression material to the material to be treated and mixing it.

[0032] When the material to be treated is soil-based, it can be treated by adding the cyanide elution inhibitor to the material to be treated and mixing. When the soil-based material to be treated does not contain moisture, it is preferable to further add an aqueous solvent prior to, simultaneously with, or after the addition of the cyanide elution inhibitor. The aqueous solvent is, for example, water such as tap water. The amount of the aqueous solvent is not particularly limited, and it is preferable that, for example, the moisture content of the soil-based material to be treated during treatment with the cyanide elution inhibitor is about 5 to 70%.

[0033] The amount of the calcined product added to the earth-based material to be treated (e.g., soil) in the cyanide elution inhibitor is not particularly limited. The amount of the calcined product added to the material to be treated can be adjusted appropriately, for example, depending on the amount of cyanide contained in the material to be treated. In addition, when the amount of cyanide contained in the material to be treated is unknown, for example, the following addition ratios can be exemplified. That is, the lower limit of the amount of the calcined product added to 100 parts by mass of the material to be treated is, for example, 1 part by mass or more, 3 parts by mass or more, or 5 parts by mass or more, and the upper limit is not particularly limited, and is, for example, 60 parts by mass or less, or 50 parts by mass or less.

[0034] The method of mixing the soil-based treated material with the calcined material is not particularly limited, and for example, on-site, mixing can be performed by stirring with heavy machinery such as a hydraulic shovel, mixing with a mobile plant, etc. In the case of the soil-based treated material, by mixing with the calcined material, for example, the cyanide ions in the soil-based treated material are insolubilized by the calcined material, so that the diffusion of the cyanide ions in the soil-based treated material can be suppressed. In addition, even if the soil-based treated material after treatment with the calcined material is impregnated with water, for example, rainwater, the cyanide ions are insolubilized by the calcined material, so that elution into the impregnated water can also be suppressed.

[0035] Similarly, the aqueous treatment material can be treated by adding the cyanide elution inhibitor to the aqueous treatment material and mixing. The amount of the calcined product added to the aqueous treatment material in the cyanide elution inhibitor is not particularly limited, and is, for example, the same as the example of the soil treatment material. In the case of the aqueous treatment material, by mixing with the calcined product, for example, the cyanide ions in the aqueous treatment material are insolubilized and precipitated by the calcined product. Therefore, for example, by removing the precipitate, the cyanide ions can be removed from the aqueous treatment material. Furthermore, even if the precipitate remains in the aqueous treatment material, the cyanide ions are insolubilized by the calcined product, so that re-diffusion from the precipitate to the aqueous treatment material can be suppressed.

[0036] According to the method for suppressing cyanide elution of the present invention, as described above, for example, the cyanide contained in the object to be treated is insolubilized by the material for suppressing cyanide elution, and therefore it is believed that the elution and diffusion of the cyanide is suppressed. However, this assumption does not limit the present invention. EXAMPLES

[0037] [Example 1] It was confirmed that cyanide-containing water was treated by the method for suppressing cyanide elution of the present invention, and the elution of cyanide was suppressed.

[0038] (1) Effect of molar ratio (Ca / Al) of fired material A calcined product (hereinafter, referred to as Ca-Al compound) was prepared from the mixture (AB) of the component (A) and the component (B). Specifically, mixtures of CaCO3 and Al(OH)3 with molar ratios (Ca / Al) of 0.5, 2, 5, and 10 were calcined at 1000°C in an air atmosphere to obtain the calcined product (Ca-Al compound).

[0039] A cyanide aqueous solution containing cyanide ions was prepared by adjusting the initial concentration of cyanide ions to 40 mg / L with water using a potassium cyanide (KCN) solution (cyanide ion standard solution 1000 mg / L, for ion chromatography, Kanto Chemical). The Ca-Al compounds having different molar ratios were added to the cyanide aqueous solution so as to be 2 g / L, and mixed. The treated solution was shaken at room temperature for 24 hours, and then the precipitate containing the calcined product and the supernatant were separated by suction filtration using a filter. The cyanide ion concentration in the supernatant was measured using a continuous flow analyzer (Synca, manufactured by BL Tech Co., Ltd.). The amount of cyanide ions removed (mg / g) per 1 g of the Ca-Al compound was then calculated.

[0040] The results are shown in Figure 1. Figure 1 is a graph showing the relationship between the molar ratio (Ca / Al) in the Ca-Al compound and the amount of cyanide ions removed. In Figure 1, the Y axis is the amount of CN removed per 1 g of the Ca-Al compound (mg / g), and the X axis is the molar ratio (Ca / Al) in the Ca-Al compound. As shown in Figure 1, all of the Ca-Al compounds were able to insolubilize and remove the cyanide ions in the cyanide aqueous solution. In particular, the closer the molar ratio (Ca / Al) was to 2, the more effectively the cyanide ions were removed.

[0041] (2) Effect of cyanide ion concentration A cyanide solution containing cyanide ions was prepared by adjusting the initial concentration of cyanide ions to 0, 6, 20, 40, or 60 mg / L with water using a potassium cyanide (KCN) solution (cyanide ion standard solution 1000 mg / L, for ion chromatography, Kanto Chemical). Ca-Al compounds with a Ca / Al molar ratio of 2 or 5 were prepared in the same manner as in (1) above. Ca-Al compounds with different molar ratios (Ca / Al) were added to the cyanide solution to a concentration of 2 g / L and mixed. Then, after shaking for 24 hours at room temperature, the precipitate and the supernatant were separated, and the cyanide ion concentration in the supernatant was measured, and the amount of cyanide ions removed per 1 g of the Ca-Al compound (mg / g) and the cyanide ion concentration (mg / L) remaining in the cyanide solution were calculated.

[0042] The results are shown in FIG. 2. The left graph in FIG. 2 is a graph showing the relationship between the amount of cyanide ions removed per 1 g of the Ca-Al compound and the concentration of cyanide ions remaining in each of the cyanide aqueous solutions after the treatment. In the left graph in FIG. 2, the Y axis is the amount of CN removed per 1 g of the Ca-Al compound (mg / g), and the X axis is the remaining CN concentration (mg / L) in each of the cyanide aqueous solutions after the treatment. The right graph in FIG. 2 is a graph showing the relationship between the amount of cyanide ions removed per 1 g of the Ca-Al compound and the initial cyanide ion concentration in each of the cyanide aqueous solutions, the Y axis is the amount of CN removed per 1 g of the Ca-Al compound (mg / g), and the X axis is the initial CN concentration (mg / L) in each of the cyanide aqueous solutions. As shown in FIG. 2, the Ca-Al compound was able to remove cyanide ions by insolubilization regardless of the molar ratio. In particular, the closer the molar ratio (Ca / Al) was to 2, the more effectively the cyanide ions could be removed, and the amount of removal was linear.

[0043] (3) Analysis of Hydrocalumite 1 Each Ca-Al compound (Ca / Al molar ratio=0.5, 2, 5, 10) in (1) was added to the cyanide aqueous solution (initial concentration of cyanide ion: 40 mg / L) to a concentration of 2 g / L, mixed, and shaken at room temperature for 24 hours. This treatment liquid was suction filtered using a filter, and the precipitate was collected on the filter. The collected precipitate was dried in a desiccator at room temperature until it reached a constant weight. The dried precipitate was analyzed by XRD (X-ray diffraction) using an X-ray diffraction analyzer to identify the crystalline compound. These results are shown in Figure 3. As shown in Figure 3, in all precipitates, the Ca-Al compound was combined with water to form hydrocalumite (Ca4Al2(OH) 14 6H2O (◇ in Figure 3) and Ca4Al2(CO3)(OH) 12 ·5H2O (△ in Figure 3) was detected. Ca4Al2(CO3)(OH) 12 5H2O is hydrocalumite (Ca4Al2(OH) 14It is believed that some of the OH in the Ca-Al compound (Ca / Al 2+ 0.6H2O) was replaced with carbonic acid (CO3) in the treatment solution or during drying of the precipitate. Hydrocalumite was formed in all of these precipitates, and the peak representing hydrocalumite was high when a Ca-Al compound with a molar ratio of (Ca / Al) = 2 was used. From this, it is presumed that hydrocalumite with a molar ratio of (Ca / Al) = 2 was efficiently formed in the treatment solution from a Ca-Al compound with a molar ratio of (Ca / Al) = 2 and water, and furthermore, this hydrocalumite effectively insolubilized the cyanide ions and removed them as precipitate. It is also presumed that hydrocalumite is formed by dissolving its OH in the treatment solution, and that the hydrocalumite is then removed as precipitate. - It is believed that a portion of this displaces the cyanide ion, thereby rendering the cyanide ion insoluble.

[0044] (4) Analysis of Hydrocalumite 2 The Ca-Al compounds with a molar ratio (Ca / Al) of 2 or 5 were added to ultrapure water at 6 g / L and mixed. The mixture was then left to stand at room temperature for 24 hours, after which the precipitate was collected and dried in the same manner as in (3) above, and analyzed by X-ray diffraction to identify the crystalline compound. The results are shown in Figure 4. As shown in Figure 4, in all precipitates, hydrocalumite (Ca4Al2(OH) 14 6H2O) and Ca4Al2(CO3)(OH) 12 Specifically, when a Ca-Al compound with a molar ratio (Ca / Al) of 2 was used, hydrocalumite (Ca4Al2(OH) 14 6H2O) and Ca4Al2(CO3)(OH) 12 When a Ca-Al compound with a molar ratio of (Ca / Al) = 5 was used, hydrocalumite (Ca4Al2(OH) 14 6H2O) and Ca4Al2(CO3)(OH) 12The compound Ca-Al·5H2O and Ca(OH)2 were detected. When the Ca-Al compound is added to water, it forms hydrocalumite. And because the molar ratio (Ca / Al) of Ca to Al in hydrocalumite is 2, it was presumed that when a Ca-Al compound with a molar ratio (Ca / Al) of 2 was used, the hydrocalumite was detected. Also, when a Ca-Al compound with a molar ratio (Ca / Al) of 5 was used, this compound had an excess of Ca relative to Al, so it was presumed that in addition to hydrocalumite, the excess Ca was detected as Ca(OH)2.

[0045] (5) Analysis of Hydrocalumite 3 The precipitate obtained by using the cyanide solution having an initial cyanide ion concentration of 6 or 60 mg / L and the Ca-Al compound having a molar ratio (Ca / Al) of 2 in the above (2) was used. The precipitate was dried and analyzed by X-ray diffraction in the same manner as in the above (3) to identify the crystalline compound. The results are shown in FIG. 5. As shown in FIG. 5, hydrocalumite was detected in all of the precipitates. The precipitate obtained by using the cyanide solution having a high initial cyanide ion concentration of 60 mg / L had a larger hydrocalumite peak than the precipitate obtained by using the cyanide solution having an initial concentration of 6 mg / L. The precipitate obtained by using the high concentration cyanide solution further contained Ca4Al2O6(CN)2·10H2O (=Ca4Al2(CN)2(OH) 12 From this result, it is believed that some of the OH in hydrocalumite is replaced by CN, and this replacement causes the cyanide ion to become insoluble.

[0046] [Example 2] It was confirmed that cyanide-containing sand was treated by the method for suppressing cyanide elution of the present invention, and the elution of cyanide was suppressed.

[0047] (1) Effect of molar ratio (Ca / Al) of fired material As in Example 1, the calcined products (Ca-Al compounds) with molar ratios (Ca / Al) of 0.5, 2, 5, and 10 were obtained. On the other hand, contaminated sand was prepared by adding 100 mg / L potassium cyanide solution to dry sand and mixing it so that the cyanide ion concentration was 10 mg / kg. The moisture content of the contaminated sand was adjusted to 10 parts by weight per 100 parts by weight of dry sand. The contaminated sand was mixed with the Ca-Al compounds so that the amount was 5 wt% relative to the weight of the dry sand used, and the mixture was placed in a filling container, the top of the container was covered, and the mixture was left to stand at room temperature for 7 days.

[0048] Each mixture after standing for 7 days was further air-dried, and the dried mixture was subjected to an elution test. That is, the mixture after standing was further air-dried at room temperature, and 100 g of the air-dried mixture was suspended in 1 L of pure water, shaken for 6 hours, and then filtered through filter paper (membrane filter with a pore size of 0.45 μm). The concentration of cyanide ions eluted in the obtained filtrate was measured using a continuous flow analyzer (Synca, manufactured by BL Tech Co., Ltd.). When all the cyanide ions contained in the contaminated sand were eluted, the cyanide ion concentration in the filtrate was 1 mg / L.

[0049] The results are shown in FIG. 6. FIG. 6 is a graph showing the cyanide ion elution concentration from the contaminated sand treated with the Ca-Al compound. In FIG. 6, the Y axis shows the CN elution concentration (mg / L), and the X axis shows the molar ratio (Ca / Al) of the Ca-Al compound. As shown in FIG. 6, the elution of cyanide ions was suppressed by Ca-Al compounds of all molar ratios. The Ca-Al compound was most effective in suppressing the elution of cyanide ions when the molar ratio (Ca / Al) was around 2. This result was similar to the result for the cyanide-containing water in Example 1.

[0050] (2) Effect of the amount of baked material added Contaminated sand with a cyanide ion concentration of 10 mg / kg was prepared in the same manner as in (1) above. The Ca-Al compound with a molar ratio (Ca / Al) of 2 was mixed with this contaminated sand to obtain a predetermined concentration (1, 5, 10, 15 wt%) relative to the weight of the dry sand used. This mixture was then left to stand for 7 days, air-dried, and subjected to a dissolution test in the same manner as in (1) above.

[0051] The results are shown in Figure 7. Figure 7 is a graph showing the concentration of cyanide ions eluted from the contaminated sand treated with the Ca-Al compound. In Figure 7, the Y axis shows the CN elution concentration (mg / L) and the X axis shows the proportion of the Ca-Al compound added. As shown in Figure 7, as the amount of the Ca-Al compound added increased, the concentration of cyanide ions eluted decreased, showing a tendency for the elution inhibition effect to increase.

[0052] Although the present invention has been described above with reference to the embodiments and examples, the present invention is not limited to the above-mentioned embodiments and examples. Various modifications that can be understood by those skilled in the art can be made to the configuration and details of the present invention within the scope of the present invention. [Industrial Applicability]

[0053] According to the method for suppressing cyanide elution of the present invention, the elution of cyanide in a material to be treated can be easily suppressed by simply mixing the material to be treated with the cyanide elution suppression material, which makes it possible to easily eliminate cyanide contamination of wastewater, soil, etc.

Claims

1. The method includes a mixing step of mixing the object to be treated with a cyanide elution suppression material, The cyanide elution inhibitor includes a calcined material (excluding gypsum), The calcined product is a calcined product of a mixture containing the following component (A) and the following component (B), which form hydrocalumite in the presence of water: the material to be treated is an aqueous or soil-based material containing cyanide, The molar ratio of Ca to Al (Ca / Al) in the fired product is 2. A method for suppressing cyanide elution. (A) Component: Ca (OH) ２ , CaCO ３ , CaCl ２ , Ca(NO ３ ) ２ At least one component selected from the group consisting of CaO (B) Component: Al(OH) ３ , and Al ２ O ３ At least one component selected from the group consisting of

2. 2. The method for suppressing cyanide elution according to claim 1, wherein the material to be treated is wastewater, soil or sludge.

3. 3. The method for suppressing elution of cyanide according to claim 1, wherein the cyanide to be suppressed is a cyanide ion.

4. The method for suppressing cyanide elution according to any one of claims 1 to 3, wherein in the mixing step, 1 to 60 parts by mass of the fired product is mixed with 100 parts by mass of the object to be treated.

5. The method for suppressing cyanide elution according to claim 4, wherein in the mixing step, 1 to 30 parts by mass of the fired product is mixed with 100 parts by mass of the object to be treated.

6. The fired product is a fired product of a mixture containing the component (A) and the component (B), The component (A) is Ca(OH). ２ , and CaCO ３ At least one of The component (B) is Al(OH). ３ The method for suppressing cyanide elution according to any one of claims 1 to 5,

7. The fired product contains CaO, Al ２ O ３ , CaAl ２ O ４ , Ca ５ A ６ O １４ , Ca ９ A ６ O １８ , and Ca １２ A １４ O ３３ The method for suppressing cyanide elution according to claim 1 , further comprising at least one crystalline compound selected from the group consisting of:

8. Including calcined materials (excluding gypsum), The calcined product is a calcined product of a mixture containing the following component (A) and the following component (B), which form hydrocalumite in the presence of water: A cyanide elution inhibitor characterized in that the molar ratio of Ca to Al (Ca / Al) in the fired product is 2. (A) Component: Ca (OH) ２ , CaCO ３ , CaCl ２ , Ca(NO ３ ) ２ At least one component selected from the group consisting of CaO (B) Component: Al(OH) ３ , and Al ２ O ３ At least one component selected from the group consisting of

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